Trifluoroacetic acid → 2-Isopropoxy-5-methyl-4-(1-methylpiperidin-4-yl)aniline

Participants

Reaction Conditions

Reaction Steps

4-(5-Isopropoxy-2-methyl-4-nitro-phenyl)-1-methyl-pyridinium iodide (Step 4, 0.697 mmol) was dissolved in CH3OH (20 mL) and cooled to 0° C. NaBH4 (264 mg, 6.97 mmol, 10 equiv.) was slowly added. After this addition was complete, the cooling bath was removed and the reaction was stirred at room temperature for 1 h. The reaction was quenched by the slow addition of 1N aqueous HCl (14 mL). The CH3OH was partially removed by vacuum. The resulting residue was partitioned between EtOAc and 1 N aqueous NaOH. Additional 50% aqueous NaOH was added until the aqueous layer had a pH>12. The EtOAc layer was washed with 1 N aqueous NaOH (2×), the organic layer was then dried over sodium sulfate, filtered, and concentrated under vacuum. After concentration, the crude product (175 mg) was dissolved in acetic acid (10 mL). TFA (0.15 mL, 3 equiv.) and PtO2 (53 mg, 30% w/w) were added and the reaction was placed under 50 psi H2 gas in a Parr Shaker for 14 h. The reaction mixture was filtered and the filtrate was concentrated under vacuum. The resulting residue was partitioned between EtOAc and 1 N aqueous NaOH. Additional 50% aqueous NaOH was added until the aqueous layer has a pH>12. The EtOAc layer was washed with 1 N aqueous NaOH (2×), the organic layer was then dried over sodium sulfate, filtered, and concentrated under vacuum to give 2-isopropoxy-5-methyl-4-(1-methyl-piperidin-4-yl)-phenylamine, which was used in subsequent steps without further purification: ESMS m/z 263.2 (M+H+).

Provenance & Evidence